1. Field of the Invention
The present invention relates to ion conductive polymers, fuel cell membranes and membrane electrode assemblies.
2. Background Art
Proton conductive polymer membranes are an important component in a fuel cell device. To achieve optimal fuel cell performance, the proton conductive polymer membrane must maintain a high ionic conductivity and mechanical stability at high and low relative humidity. Aromatic perfluorocyclobutane random copolymers have been disclosed in U.S. Pat. No. 6,559,237 as improved membrane materials for fuel cells. Due to the chain configuration of random copolymers, however, water swelling at high humidity and membrane shrinking at low humidity are common problems with random copolymers. A random copolymer membrane lacks the mechanical robustness to withstand the rigors of hydration and dehydration within an operating fuel cell.
Accordingly, there is a need to provide a further improved proton conductive polymer membrane that maintains robust mechanical properties and high ionic conductivity at wide range of humidity conditions.